This invention relates to optical switching networks in general, and more particularly to a lens controller and a fiber controller for independently positioning each element relative to one another.
Often it is desirable to have a relatively small switching fabric for a variety of purposes, such as optical add-drop or small switching fabrics for all-optical networks. A variety of techniques have been used for this purpose. For example, it is possible to use micromachined moving mirrors for free space optical switching devices. Mirrors inserted between collimators may be used to switch the beam around between the collimators. Likewise, it is possible to move the fiber in front of the collimator lens and thereby steer the beam from one collimator to another. This actuation may be done by using piezoelectric, magnetic or other means. Or, conversely, the collimator lens may be moved in front of a stationary fiber to achieve the same beam deflection, with similar actuation mechanisms if desired.
It is generally very important that such actuation mechanisms not be affected by vibrations that may occur in the environment of the switch. In addition, in order to make the fabric expandable, it is generally important that the elements of the fabric not be affected by vibrations that occur during module insertion, which is used to expand the switching fabric. It is also important that the insertion and proper docking of an expansion module occurs in an environment that requires a minimum amount of environmental protection so as to make the insertion mechanism simple and inexpensive. In this respect it should be appreciated that the ability to expand a modular fabric during operation allows for a low entry cost of the whole array. Therefore, it is generally quite desirable to construct a switching fabric that has very low loss, and has a low cost, and that can be expanded on demand to a relatively large size (e.g., 256xc3x97256).
By providing two independently controlled piezo actuators, oriented along axes orthogonal to one another and moving in directions orthogonal to each other, it becomes possible to move both the lens and the fiber independently of one another, and in such a way that the beam can be displaced over a large field. Vibration control is thereby vastly improved for vibrations caused by both environmental factors and module insertion. This allows for relatively simple module insertion during operation and, therefore, allows for fully modular assembly during the operation of the switch fabric. The control system is also considerably simplified due to the absence of mechanical or other coupling between the two axes. The use of a bending unimorph, bending bimorph, or another similar actuator further assists with control because such actuation tends to excite only the desired mode and does not tend to excite higher modes. This is a significant feature, since the control and damping of higher modes, once excited, generally requires more elaborate sensing and control mechanisms.